CNC Machine

CNC Cutting

By: Josh Rucinkski

More news from the CNC table.  My confidence has grown as the graduate studio has placed more work on the CNC table and I am going to try to lay down a few pointers.

1.    Always save your 2D cutting files as AutoCAD 2012 or earlier.  The CAM software shopbot uses can read CAD pretty well.

2.    Never have splines in your final output.  Shopbot can see splines, but they are very primitive, really just nodes with lines going from point to point.  It is okay to use splines to make your shapes and this does save your computer processing time, but use the pedit command them at the last stage to convert them to polylines.  You can also use the command convert.

3.    Pocket cuts MUST be closed ploylines to be 'seen' by the CAM software.  Having Polylines that end and start at the same place is not good enough, you must close them by checking the closed checkbox in the properties pane in AutoCAD. Use a similar notion if you prefer using a different program to export to CAD.

4.    Which brings me to the next point, use AutoCAD for final authoring.  I have cut pieces exporting .dwg files direct from Rhino, but it meant some wasted time at the CAM station.  Rhino does not save .dwg files the same as AutoCAD.  I think it is safe to say you cannot expect different from other non-AutoCAD sources.

5.    A Rhino tip, export .dwg as 2004 Natural.  That will NOT break the model into billions of separate angular line segments.

6.    3D cuts are .stl files.

7.    3D cuts should contain the base matter that surrounds the model. ?! It means this, imagine you are cutting a dome shaped from a square shaped foam blank.  If you only have a dome shape, the CNC will cut everything except the dome, so the time is wasted as the CNC cuts a lot of foam cleaning out the corners of the square shape.  On the other hand, if you include the blank in the shape and say only have a small ring of material cut out around the dome, the cut will save you a lot time. Because the CNC only removed the parts that define a dome and a tight cutting ring around the dome to free it.

8.    Save different depths of cutting as seperate layers and use colors.

9.    Be prepared to stay awhile, CNC takes more time then the laser cutter, and a representative must be present during cutting.  Unlike the laser cutter, the CNC has a lot of intent behind choices like depths of cut and they may need to be adjusted as the CNC is running.  Telling the computer I want a 0.125” cut might seem shallow in the mind, but may be too large for comfort when looking at it actually cut out.

10. Be patient.  The CNC is an impressive and powerful tool and it needs careful review before proceeding.  Zeroing the tool, Changing tool heads, making screw marks for holding materials all take more time then the other digital fabrication tools, but it is well worth it.  Only the CNC can bring full scale to life!